This invention relates to energy absorbing apparatus for preventing a vehicle from impacting a stationary structure. More particularly, this invention relates to a reusable impact attenuation device designed to absorb and dissipate the impact energy of a colliding vehicle or the like.
It is known to position energy absorbing devices along highways and the like to prevent vehicles from impacting stationary structures such as bridge abutments, parapets, signs, traffic dividers and rigid guardrails. Many of these devices suffer one or more of the following disadvantages: they are not reusable; they are difficult to repair or restore; they rebound the impacting vehicle back onto the highway where it may collide with other moving vehicles; they are expensive; they are not readily able to absorb the impact energy of a head on impact; and they occupy an inordinate amount of space.
Reusable energy absorbing devices have been developed. Some of these reusable energy absorbing devices suffer from the drawback of requiring either (1) that the energy absorbing material must be replenished within the barrier after an impact, or (2) that the portion of the apparatus which has been crushed by the impact must be replaced or repaired. Some of these reusable energy absorbing devices also suffer from the drawback that they require an inordinate amount of space and are difficult and expensive to restore to a useful condition.
One of the major problems in constructing any energy absorbing device is the problem of rebounding. When a compressible material reaches the end of its compressive stroke the material tends to rebound. This rebound can throw an impacting vehicle back into traffic, and it can injure the occupants of the impacting vehicle.
Thus, there is a need for a reusable impact attenuation device which has little rebound, is easily restored after an impact, and does not require an inordinate amount of space.